Erythromycins are antibiotics clinically widely used as agents for treating infectious diseases caused by Gram-positive bacteria, some Gram-negative bacteria, mycoplasmas, etc. Many erythromycin derivatives have been prepared for the improvement of biological and/or pharmacological properties of erythromycins. Examples of prior art 5-O-desosaminylerythronolide derivative are 3-O-acyl-5-O-desosaminylerythronolide derivatives described in U.S. Pat. No. 3,923,784. However, prior art 5-O-desosaminylerythronolide derivatives are generally considered as inferior in the antibacterial properties, and actually, the above-mentioned derivatives have extremely weak antibacterial activity. An object of the present invention is to provide novel antibiotics having a strong antibacterial activity.